Netgear provides the same firmware for both routers. I can confirm that I have insatlled OpenWrt on my R6230 following the R6220 wiki page without any problems. How should this be reflected in the supported devices documentation? Does there need to be something more concrete for it to be "officially" supported? I don't want to go and edit wiki pages randomly, but I think there should at least be a mention somewhere that installing OpenWrt is possible with the R6230.
I wouldn't consider it "random" to state that Netgear provides exactly the same firmware for both units and that
This R6230 is likely internally identical to the Netgear R6220 since Netgear publishes a single firmware update for both models and no new FCC ID can be found for the R6230.
with an appropriate warning that, although successful on at least one unit, that it is at the user's own risk.
You could mention this on the 6220 devicepage and create a dataentry for the 6230.